Radio communicating system



May 31, 1949; E. M. DELORAINE ET AL 2,471,415

RADIQ COMMUNIGATING SYSTEM l Filed March 28, 1946 5 Sheets-Sheet 1 DON/M0 D. G/P/EG ATTORNEY May 31, 1949 E. M. DELORAINE ETAL. 2,471,416

I RADIO COMMUNICATING SYSTEM Filed March 28. 1946 3 Sheets-Shed'.I 5

foMoA/o M. mom/wf 00A/ALD o. G/P/EG BY ATMP/VFY The two terminals including the chain of repeater stations may be connected by radio links which may include directional or line-of-sight transmitting and receiving antennas between each of the repeater stations or they may be connected by a transmission line such as a coaxial cable for transmitting high frequency waves.

The repeater stations should not only be equipped to receive and transmit the multichannel wave along the route to the next adjacent repeater station in one or both directions, but also to transmit signals to adjacent vehicles along the route as well as to received signals from those vehicles. In order to prevent interference between two adjacent repeater stations the signals transmitting therefrom may preferably have directivity such as transmission and reception only in one semi-circular area of 180 perpendicular to the route. Each repeater station is provided with separate transmitter and receiver circuits for the wave traveling from the west terminal and for the wave traveling from the east terminal. If desired, the wave traveling from one or both terminals may be completely or partially transmitted to the vehicles from each repeater. The wave from the west terminal may be all or partly transmitted to the vehicles, and wave from the east terminal may contain time spaces for signals received from the vehicles. In this case the marker or synchronizing pulses on the wave from the east terminal should be transmitted by the repeater so that the signals from the vehicle may be synchronized and inserted in the proper spaces on this wave. On the other hand, the wave traveling in one direction may carry signals both for transmission to the vehicles as well as time spaces for pulse modulated signals transmitted from the vehicles while the multichannel wave traveling in the opposite direction from the other terminal may not be transmitted from any of the repeater stations to any vehicles along the route but merely act as a return for the multichannel wave transmitted from the main station.

Each of the vehicles along the route, in order v to take advantage of the communication system of this invention, should ce provided with a suit able radio transmitter and receiver for receiving the signals from the nearest repeater station and a transmitter for transmitting its own signals back to that station. In the first aforementioned system, wherein all of the multichannel wave traveling in one direction is transmitted to the vehicles and only the synchronizing pulses of the wave traveling in the other direction are transmitted, there may be provided a separate means for receiving the synchronizing pulses. Each vehicle is assigned a definite time space channel on the multichannel wave traveling toward the main terminal, which space has a deiinite time relation to the position oi marker pulses on that wave. Therefore, each vehicle is provided with means for synchronizing its transmitted signals in timed relation to the received marker pulses so that when it is fitted at the repeater terminal on the main returning multichannel wave the signal from the vehicle will fall in the position reserved for that vehicle, and not interfere with other signal channels on that wave. To insure proper tting or placement of the vehicle transmitted signal on the main multichannel wave, the marker or synchronizing pulse transmitted from that wave to the vehicle is again transmitted with the signal from the vehicle in the pre-selected or assigned proper time spaced relationship. Furthermore, in order to prevent interference between signals from two or more vehicles transmitting to the same repeater station, the signals from each vehicle should have a different identiiying characteristic, such as the shape or width oi their pulses or the frequency of the carrier waves therefor.

Each repeater station is provided with means for selecting the signals from the different vehicles and automatically and continuously measing their distances by means of the delay of the transmitted and again received marker pulses, so that the signals transmitted from the vehicles will be adjustably delayed regardless of their distance or change in their distance from that repeater station. Each repeater station is also provided with separate inserter circuits for each one of the Vehicles which may transmit signals to it as it travels along the route, since each vehicle has a different assigned timed space position or channel on the multichannel pulse wave. Thus, different delayed constants in the inserter circuits are provided corresponding to the time space channel from the marker reserved for each vehicle.

While this invention itself is defined in the appended claims, the foregoing and other features and objects of the invention will become more apparent and the invention best understood upon consideration of the following detailed description of an embodiment of the invention to be read in connection with the accompanying drawings, in which:

Fig. 1 is a schematic block diagram of the multichannel communication system of this invention showing the stations and terminals along a route;

Fig. 2 is a schematic block wiring diagram of one of the repeater stations shown in Fig. 1;

Fig. 3 is a graph of wave forms useful in eX- plaining the operation of the circuits in Figs. 2 and 6;

Fig. l is a schematic block wiring diagram of the circuits for a Vehicle traveling along the route of Fig. l;

Fig. 5 is a graph of wave forms useful in eX- plaining the modication of the vehicle selector circuits shown in Fig. 2;

Fig. 6 is a schematic wiring diagram of a modification of the distance measuring circuit shown in Fig. 2.

For convenience, the description is defined into the following chapters: Chapter I-The route system; Chapter II-The vehicle circuits; Chapter III- The repeater circuits; and Chapter IV-A modified system.

CHAPTER I The route system Fig. l shows the essential stations located along a route for communicating with vehicles traveling along that route according to this invention. At each end of the route there is located a terminal station, one of which may be a master or main terminal station, which in this case is the west terminal l. At the other end of the route is the east terminal station 2 which may be also a master station or may merely return the signals transmitted to it along the route back to the west terminal l. In between the two terminals are provided repeater stations 3 located at suitable distances along the route both for relaying signals along the route in each direction toward each terminal, as well as for relaying the signals to vehicles within their range.

I envia-11e Illfief'linlrcmeans Vor mediumfor transmission of-"the signals between terminals I and 2 and v"through-repeater stations 3 maybe by radio or Mcable. If radio is employed the repeater' anten- -nas may have-directivty so that their signals will not be confused with the signals transmitted "andreceived from the vehicles along the route. Forthis'case an ultra-high frequency wave, that lis;l a line-of-sight Wave may be used and the repeater stations may be placed on high ground or towers, say every 20 or 30 miles apart.

Thetermin'als also may be provided with cirj'cuitssimilar to those vemployed in the repeater "stations `for transmitting and receiving signals "from-vehicles closest to them.

v As npreviously mentioned, the signals transmitted* along the route are'imodulated on pulses tdformtrains of pulse modulated signals, Which ytrains are" interleaved on a single wave with "marker or rsynchronizing pulses similar to wave 4"'shown`in Fig. 3. I-Iere the different channels a; b, c form a group of pulses which have "'de'nite time spaced relationships with respect to the interleaved marker pulses M. Such a wave 4 may have unoccupied channel spaces, such as forsignals d and e, from vehicles along the route. The` diiferent signal channels a, b, c, may be "directly induced in the pulse modulator circuits 5`or may be passed through a suitable switch- 'board @,Which may be connected to other signals `received from points along the route or from outside sources to lines 1. The resulting multi- "channel electro-magnetic pulse modulated wave 4'. produced in the circuits 5 may be withdrawn "through line 8 into a transmitter l0 for trans- ""mission along the route over suitable link medium 'or means I I passing through repeater stations 3 to the east terminal 2. If the frequency components of the multi-channel pulse wave l are suiiiciently high the modulation of the pulses l on a carrier wave of higher frequency is not necessary for their transmission. lHowever, throughout this and particularly other parts'of thesystem it is desirable to employ radio carrier waves of different frequencies for the signals traveling in different directions as well tas for the signals transmitted and received in the repeater stations.

The repeater stations 3 may comprise suitable radio antennas IZ for transmitting the signals received over means I I directly to the vehicles along the route. This may be accomplished in a suitable eastbound repeater circuit I3 (Fig. 2) from which the incoming wave 4 is transmitted vto* vehicles, such as airplanes P-I and P--Z on the same or a different frequency carrier wave yasthat received from the west terminal i through line II. The circuit I3 also amplies the multi- `y`channel `pulse wave 4 before transmitting it on "through the line II to the next station along the ^route.

'Ihe east terminal 2 may -comprise a receiver I4 which is directly coupled through line I5 to a transmitter I6 for transmitting the same wave i back along the route over a suitable link means -;I'I `.(similar to II )'through the same repeater stations 3. The east terminal 2 may comprise also: complete modulator and demodulator cir- J-:cuits similar to those shown in the West terminal '.I, and mayv be connected with signals from outiside; sources not shown) It is-desirablethat'means I'I loe-separate from lz-.Hmeans II-,such as a different carrier wave frequency from i that produced= ink 'transmitter I 0 in Y the west i terminal, iso that yse-parationw may:r be made between the waves passed in each'direction by the vehicles along the route. However, in the modified system described later in Chapterl'IV, separate frequencies are not -necessary provided the paths of link-means II and Il are separate such as two coaxial cables.

For convenience in the description of -this embodiment of the invention the frequency of the east terminal carrier wave will be referred toV as fi andthat of the west terminal carrier wave will be referred to as f2. In order to fdistinguish the signals received from the airplanes P-I and P2, they transmit signals in still different frequencies f3 and f4 (as shown in Fig; 2) which are received at repeaters 3 on antennas 29 coupled to the westbound repeater circuitsll.

The returning or westbound multichannel pulse-modulated wave 4 from transmitter I6 through medium I1 is passedthrough a suitable westbound repeater circuit I8 (in Fig. 2)'fir1 each repeater station 3. This received wave of different frequency f2 may be all or partially transmitted from the repeater I8 through antenna v4I9 to the vehicles but preferably only the synchronizing or marker pulses M are transmitted. The transmission of these synchronizing pulses isffor quasi-radar purposes to measure the distance between that repeater station and the vehicle `in its vicinity transmitting to that repeater, for operation of the inserter circuits later described and comprising part of the westbound repeater circuit I8. The signals received from the vehicles are automatically delayed and inserted in the vacant channel spaces d and e on wave it before the resulting westbound multichannel wave is transmitted on toward the west terminal through medium Il.

The resulting multichannel wave from the east terminal and repeater 3 is received at the west terminal I in a suitable demodulator cir-cuit 22 from which the signals d and e from airplanes P-I and P-2 may be demodulated and passed through the switchboard 6.

The modulation and demodulation of signals on pulses according to the system of this invention may be with respect to time or amplitude. Suitable systems for time modulation and demodulation are described in the copending applications of: E. M. Deloraine and N. I-I. Young, Ser. No. 504,204, Sept. 29, 1943; E. M. Deloraine and J. L. Fearing, Ser. No. 506,802, Oct. 19, 1943, yPatent No. 2,429,613, dated Oct. 28, 1947; D. D. Greig, Ser. No. 536,301, May 19, 1944; D. D. Greig, Sei'. No. 539,856, June l2, 1944, Patent No. 2,424,977, dated Aug. 5, 1947; D. D. Greig, Ser. No. 625,650, Oct. 30, 1945; E. Labin et al., Ser. No. 591,065, Apr. 30, 1945, Patent No. 2,429,631, dated October 28, 1947, and E. Labin et al., Ser. No. 565,152, Nov. 25, 1944, Patent No. 2,465,380, dated Marchv 29, 1949.

CHAPTER II The vehicle circuits Each vehicle, in order to make full use of the advantages of this system, should be provided with a receiver and a transmitter circuit similar to that shown in Fig. 4. For this embodiment,

the f1 eastbound multichannel wave transmitted from antennas I2 of the stations 3 is received over antenna 23 and coupled to a suitable-'receiver 24 from which is withdrawn the wave 4 through line 25 into the marker pulse selector circuit"`26 (similar to that shown in copendingapplicationof D. D. Greig; SerrNo; 625,650jf1ledOctoberi30,

i945) for separating the marker pulses M from the other pulses on the Wave d. These separated marker pulses are then passed into the suitable Wave generator 21 for producing a base wave which is then passed into a suitable delay device, 28, which may in the case of a sine wave be a phase shifter, for delaying the Wave an amount corresponding at the time interval channel to be selected by the vehicle, such as a, b, c, etc., indicated by the contacts 29. (If desired, additional delay devices may be employed on each vehicle for simultaneously selecting additional channels communicated thereto.) The resulting delayed Wave in device 2B is then passed into a suitable pulse demodulator circuit S which is also connected through line 3Q to the wave i from receiver 24. The delayed wave in circuit 9 deblocks the selected channel of pulse-modulated signals so it may be demodulated, are Withdrawn through line 2l, as, say, signal a.

In the present described embodiment, there n also may be provided on the vehicle a second ren ceiver for the synchronizing pulses from the Westbound multichannel Wave for the purpose of both synchronizing the channel or channels transmitted on the vehicle as Well as continually measuring the distance to that vehicle. Referring back to Fig. 2, the transmission of the marker pulses M from the Westbound Wave may be accomplished by receiving the Westbound wave in a suitable receiver 32 and passing the wave through the line 33 to a suitable marker selector Bil (similar to Selector 26 in Fig. 4) and then passing the selected marker pulses (shown on Wave 35 in Fig. 3) through line 36 to a suitable transmitter 3l coupled to the antenna i9. The frequency of this transmitter may be the same as that of the Westbound multichannel Wave, namely frequency f2.

Due to the distance between the plane P-l and the repeater station transmitting the marker pulse Wave 35, the pulses on the Wave 35 are de layed in time as shown by the wave 38 in Fig. 3. For illustration, it is assumed that the plane Pi is farther away from the nearest repeater station than the plane P2, and that the plane P-i is traveling in the direction toward that repeater station While the plane P-i-Z is traveling away from the repeater station. Thus, successive pulses received by the plane P-l' will be delayed in time less and less as the plane approaches. graphically represented on Wave 3S by showing the rst marker pulse received from the Wave 35 delayed a time t1 while a later manier pulse is delayed a time t1 less than the time ti. Similarly, a still later pulse is delayed still lefs time t1" closer to the repeater station than plane P-i but is traveling away from the repeater station, the marker pulse from antenna i9 will be delayed only in time tz (shown on the Wave 3S in Fig. 3) While a later pulse will be delayed a time t2' and a still later pulse a time t2, wherein t2" is greater than t2' is greater than t2.

Referring back to Fig. 4 and assuming that the circuit is on the plane P-L the Wave 38 may be received over antenna il@ coupled to f2, receiver 4l and thence passed to a wave generator lf3-2 through line 43. If desired, one receiver and antenna may be employed for receiving both Waves f1 and f2, if it is tuned to suciently Wide frequency range, and the resulting received signals may be separated in filters (not shown). The resulting received pulse Wave 33 produces in generator 42 a suitable modulating wave which may be delayed in the device 44 (similar to device 28) but it is delayed in time corresponding to the channel selected for the plane P-I, in this case channel d of contacts 45. The thus delayed wave is then passed through line 46 to a suitable pulse modulated circuit il upon which the signal d, introduced to line is pulse modulated to produce a train of pulses d spaced in time trom the marker pulses on Wave 33 a distance according to the distance between the marker pulse M and the vacant channel space d on Wave Il. The resulting train of pulses d is passed through line 49 into a mixer 5@ Where it is mixed with a train of marker pulses MP1 produced in the marker pulse generator 5l controlled through line 52 by the received pulse wave t8. From the mixer 5i) is then Withdrawn the wave 53 (Fig. 3) which is then passed to transmitter 5t, preferably operating at a different frequency than any of the others previously mentioned, such as frequency of f3. The wave 53 is then returned from the antenna 55 back to the repeater station and received on antenna 2U the pulses on which are further delayed in time according to the times t1, t1 and t1 previously mentioned.

Similarly, the marker pulses from the antenna ia of the repeater station are received in delayed times t2, i2 and t2 as shown on Wave 39 at the airplane P-Z and are thus passed through the left portion ci circuit shown in Fig. 4 to produce a train of channel pulses e and marker pulses Mp2 which are mixed to produce the wave 55. Channel e, being the channel reserved for plane P-2, is selected in the device by adjusting it to Vcontact corresponding to channel e to delay the pulses e with respect to the marker pulses MP2 time corresponding to the time spacing between marker pulse M and space e on wave 4.

The receiver 5l, in the westbound repeater circuit l, coupled to antenna 2E) thus detects pulses irom both planes P-l and P-Z to produce the pulse wave 58 shown in Fig. 3, which is a mixture of Wave e3 and 555 delayed respectively in times 21h, Ztl', Ztl", and Zta, Etz', Zta".

In order to prevent confusion and in order to identify the diierent Vehicles the waves 53 and This is J "I 58 transmitted from the vehicles, their identifying characteristics instead of being their different carrier frequencies fa and fr may be in the Width of their pulses, such as shown in the graph in Eig. 5. Tlflerein the pulses from plane P- are shown to have a greater width than those from plane P E, Waves 59, @il and Si corresponding to the Waves and 58 in 3, respectively. The references to the pulses shown in Fig. 5 are primed which is less than tu For plane P Z which is so that tney may be compared with the reference characters to the pulses shown in Fig. 3.

The pulse demodulator and modulator circuits shown in Fig. 4 may be similar to the circuits 5 and 22 mentioned in Fig. l or similar to those disclosed in the above mentioned copending application of E. M. Deloraine, Ser. No. 531,851, filed April 20, 1944.

CHAPTER III The repeater circuits Referring nov/ to the automatic inserter circuits lr, tl, etc., in the westbound repeater station, circuits lu shown in Fig. 2, a separate inserter circuit is provided for each of the vehicles traveling along the route, P-l, P-2, etc., respectively. Each of these inserter circuits includes a vehicle or plane selector circuit 65, a marker selector circuit 6E (similar to 26 in Fig. 4), and a distance measuring circuit 61.

Thevehicle (selector circuits dit` may :comprise f .-.iilters/,to separate the Adiiierent,carrier, frequencies correspondingfto-thediiierentvehicles. For example, plane P-L'transmitsk the :wave tillY on` a Y., carrier `frequency f3... aiselectorl 65., may comprise a. `filter. for .passing onlypulses modulated on-the `J- frequency, wave. If thepulsesffrom. plane P-l have a given-width.characteristic ,as shown on --Wave-59 in- Fig. 5, vthe select/0h65 may comprise a Width selectorv circuit;.similar,to thatfdescribed .and;shown in Fig; 8V inthe copending application Aof l\/l..Deloraine,Y Seria-LNQ. 531,851, :mentioned above.

- The resulting selected pulsey waves correspondingto planes .P-l and P,-2 are shown as waves ,68vand I69respectively in Fig. 3 -wherein each of the pulses are ldelayed twicethe time they are rdelayed in waves 38 and 39 above, since they, have I, now traversedv twice thefdistance betweenY the planes ,and the repeater station. As shown in Waves.iiandeo, the pulse trainsv are out oil-:phase with the wave 4 and thei7 must, herelativelyadkvvanceol or delayed so that the marker pulses MP1 and vMP2 will superimpose with the marker pulses M on the wave 4. This is `automatically accomplished in the distance measuring circuit t1. The

marker pulses vMp1 andMPz from waves B8 and ,69 are ,separatelyselected incircuits 66 so that theymay -beicompared with thev marker pulses transmitted romthewestbound wave .ll separated in selector 34 andtransrnitted to the vehicle from duce the wave i3.

-antenna I9.

n Referring specically to the pulse inserter cir- U,cuit 52 for plane P-i, the. wave- ,lil is Withdrawn Yfrom,tl'iewmarker .selector 5G Ycomprising pulses correspondingtomarker pulses Mei on Wave. 58. This distance orI timedelay between them and rmarker pulses on wave ,35. iscbtained by--mixing the, pulseWaVe t5 frornselector 34 through line 'Il in the,mixer l2 (of the' distance measuring circuit 57) with wave Z9 from selector 66 topro- This wave i3 iswithdrawn through line M. for triggering a suitable multivibrator or similartrigger circuit `'lto produce thev wave iii. ,The positive pulses ,on thewave 7E correspond in width. to the diierent distances of the plane P-l from the repeater Station. at

,diferent times.

, If wave i6 were passed through a. suitable Atranslator circuit "il, which may comprise a lt-er or a generator to produce waves of different amplitudes corresponding to the Iwidth of the pulses 75, a change in the flow of energy can be obtained ycorresponding to the change in distance of the plane P-l' from thev repeater station. This "change in energy may be passed through a suitabile means for variably changing the delay caused by passing the signal pulses received from y'P i through an articial' delay line 18 compris- -ing a network vof inductances 19 and condensers "8o. "The lin'ductances "i9 may be connected through a suitable magnetic core 8l vthrough thenetwork ,mils withdrawn .the properly delayedy pulse wave @il upon which themarker pulses ,MP1, and, delayedtimes-Tpiand TPi, so4 as to ,coincidayfith the,.rn a1gker DUlSesMl .omit/We 4,

V10 The resulting ,wave is .passed through .line into a suitable mixerfclipperu in which,;,is produced the wave 8l composed of waves-:Mend

wave i from receiver 32. The tubes tnot shown) of the: initier clipper '.86 may be biasedto vclip a double amplitude marker :pulse'88 from the wave 8l above the line 89, so that only thepulsesfroccurring below theline on wave S'lswillfbe passed `from the'mixerrclipper e36 Athrough the line Si@ to the westbound transmitter` 9|. illflis transmitter may operate the same 'frequency f2 the wave receiver inl circuit,-32,f.;andfitf-lmay transini the wave. i now containing thepulse modulated signals from plane P--l on tothe 'West terminal l.

Instead of a lter translator 11 operatingI actov energy the-Variable width :pulses or wave '.i a circuit may: be providedbsimilarrto that shown in Fig.A 6 wherein the wave-116 is introduced through line 92 into a phase inverters93 to produce the wave Qt shown in Fig. Wave is then passed into asaw-tooth wave-generator circuit et comprising a'tube '95 and-condenfser jtroni which circuit is withdrawnthe saw-,tooth rave el through line 98 for connection-tothe inductance coil 32 of' the delay deviceelfot should loe noted that the amplitudes h, hi; husof the saw-tooth pulses on wave y971correspond-respectively to the wdthsZti,A 2t1,2t1- on'wave'fl'.

if desired, inserter circuits similar to--.\,62,=:63, Fitshoivn in the repeater sta-tions, rmay'also be provided in either orf-.bothterminal#circuitsz-so that pulse trains received on hthe multichannel wave may be directly transmittedagainonrthe outgoing multichannel wave withoutv demodulation and modulation, once their identification and destination is determined hy'the--operator-atff the terminal. 1n such a case a manually adjustable delay device could be provided at'the terminals, nsteaci of the variable delay device 'lshownf'in VFig 2. which would/be similar to the delayzdev-ices shown at 28 or M in Fig. 4.

CHAPTER IV A modified system Instead of transmitting-all or a portion of,..both the eastbound and westbound ymultichannel Waves traveling through mediums il :and Hain l, the multicl'iannelv waves traveling-only, in one direction may he transmitted and Vhavesignais from the vehicles'insertedV thereon, thereby eliminating additionaltransmitter and receiver circuits i2 and iii at the repeater and at Ythe'veliicle, respectively. In order rto change'thel systern of the embodiment above described intoa system such as this, the closed switches l'shown in Figs. l, 2 and 4 are opened, and correspond- 1ngly the open switches are closed.

)In the repeater stations 3 the switches-99 `are opened so that the Wave traveling along themedium l i will merely -be relayed from one repeater station to the other without being transmitted to the vehicle along the route. Also in each repeater station the switch lili) in line 33 isppened and .switch iti is closed to 10V-pass the marker selector 3d (shown in Fig. 2) so that all of ythe wave i will he transmitted at the vehicle over antenna i9- On the vehicle the selector marker pulses, on the received wave may. beemployed both for Adeblocking and demodulation ,ofthe ,selected ,Signal channels to the vehicle, as wellas forsynchronizingthechannel to .be transmittedillom,Iheyehicle. In this case the Vehicle circuit shown in Fig. 4 would have the switch H32 open and the switch l 93 closed, so that the selected marker pulses also pass through line lim to the transmission circuit. This marker pulse would then operate marker pulse generator 5| and may also operate the wave generator 42. However, if desired. only the wave generator 2l may be employed and its output may be connected to both the delay devices 2S and 44 (not shown). The operation of the switches E02 and |03 in Fig. 4 cut out the receiver circuits 4D and 4| which eliminates the necessity of transmitting signals at two different frequencies from the repeaters to all the vehicles along the route,

This system also has the advantage of reducing the number of carrier frequencies required for the same amount of information communicated in the first described embodiment.

Another modication of this system may be similar to that shown in Figs. 13 through 17 in the above mentioned case of E. M. Deoraine, Serial No. 531,851, wherein different width pulses may be provided for different repeater stations or group of repeater stations along the route for transmitting certain channels of signals to certain vehicles and receiving signals from those vehicles for insertion into the same channel spaces along the same transmitted wave as the selected channel signals are transmitted to the vehicles.

While the above is a description of the principles of this invention in connection with specific apparatus it is to be clearly understood that this description is made only by way of example and notas a limitation on the scope of this invention.

We claim:

1. A communication system for mobile stations moving along a route comprising: a main station for transmitting a multichannel electromagnetic pulse wave having given reserved pulse channel positions for the insertion of pulses from said mobile stations, means for transmitting said wave along said route including a chain of repeaters for transmitting at least selected channel pulses of said wave to vehicles along said route and receiving pulse Waves including signal modulated pulses from said mobile stations. said repeaters including means operative under the control of said selected channel pulses and said pulse Waves from said mobile stations for inserting the signal modulated pulse waves from said mobile stations in said given reserved positions on the original pulse wave transmitted from said main station. and means for returning the resulting multichannel signal modulated pulse wave to said main station.

2. The system of claim 1 wherein said main station includes means for producing marker pulses interleaved at regular intervals along said multi-channel pulse waves and said repeaters include means for transmitting to said mobile stations said marker pulses from at least one of said multichannel pulse waves for automatically measuring the distance between said mobile stations and said repeaters.

3. The system of claim 1 wherein said inserting means in said repeater stations include means for automatically measuring the distance between said repeaters and Said vehicles.

4. The system of claim l wherein said inserting means in said repeater stations include means for continuously determining the distance between said repeater stations and said vehicles and automatically controlling the amount of delay of the waves received from said vehicles by l2. said determined distances to continuously insert the received waves in the unlled channel spaces on the original multichannel pulse wave passing through said repeater stations.

5. A system for continuously communicating with vehicles along a route comprising: a main station for producing a multichannel signal pulsemodulated electromagnetic Wave having different recurrent time interval spaces therealong for different signal channel pulses and having marker pulses regularly interleaved between similar groups of channel pulses, a chain of repeater stations extending along said route, means for transmitting said wave through said repeater stations and from said repeater stations to said vehicles along said route, means on said vehicles for receiving said wave and separating the marker pulses therefrom, further means on said vehicles for transmitting a channel of pulse-modulated signals controlled in time with respect to said received marker pulses and retransmitting the marker pulses, and means in said repeater stations for receiving the signals, means operative under the control of the marker pulses of the original wave and the retransmitted marker pulses for interleaving said received signals in a given space interval on said Wave.

6. 'Ihe system of claim 5 wherein said inter leaving means in said repeater stations include means for automatically measuring the distance between said repeater stations and vehicles by use of said marker pulses.

'7. The system of claim 5. Where said interleaving means in said repeater stations include means for automatically delaying the received signals from said vehicles in accordance with the distances of said vehicles from said repeater stations.

8. The system of claim 5, wherein said means for producing pulse-modulated signals includes f1 means for time modulating said pulses in accordance with said signals.

9. A multichannel communication system for communicating with vehicles moving along a route comprising: a main station for producing a multichannel-signal pulse-modulated electro magnetic wave having different recurrent time interval spaces therealong for pulses of dierent signal channels all of which spaces are not filled with pulses and having marker pulses regularly interleaved between similar groups of different signal channel spaces, repeater stations along said route for transmitting said waves both along said route and from said station to vehicles along said route, means on said vehicles for receiving said wave and for transmitting a different signal modulated pulse wave to the repeater stations from which they receive said multichannel wave, said repeater stations including means for receiving said different pulse waves and automatically inserting said different pulse waves in the unfilled spaces on said original multichannel pulse wave, said means on said vehicles including means for transmitting the signal modulated pulse waves therefrom together with the received marker pulses and synchronizing said transmitted clifferent signal modulated pulse waves with said received marker pulses, and said inserting means in said repeater stations including means for selecting said marker pulses from both the received and transmitted waves at said repeater stations in order to measure the distance to said vehicles, and means controlled by the resulting measured distance for inserting the reecived waves from said vehicles Iin the unlled channel spaces on the original multichannel pulse Wave passing Number Name Date through said repeater stations. 2,155,821 Goldsmith Apr. 25, 1939 EDMOND M. DELORAINE. 2,171,293 Plastino Aug. 29, 1939 DONALD D. GRIEG. 2,248,727 Strobel July 8, 1941 5 2,262,838 Deloraine et al. Nov. 18, 1941 REFERENCES CITED 2,406,165 Schroeder Aug. 2o, 1947 The following references are of record in the 2,421,017 Delorame et al May 27 1947 me of this patent; 2,421,727 'Thompson 11 June 3, 1947 UNITED STATES PATENTS 10 OTHER REFERENCES Number Name Date Pennsylvania Turnpike, Electronics, May

1,394,019 Buckley Jan 10, 1933 1942, pp. 34 t0 51. (Copy in 250-15.) 

